provision of housing without appropriate enrichment).4 In order to prevent poor or deteriorating welfare, researchers, animal care staff, and institutions have a responsibility to provide high-quality care for laboratory animals, including ready access to fresh water and a nutritive diet; an environment that ensures shelter and comfort; prevention as well as rapid diagnosis and alleviation (as appropriate) of pain, injury, and disease; species-appropriate space, facilities, and (if appropriate) companionship; and conditions and treatment that do not cause negative emotional states. Fraser and colleagues suggest that good animal welfare implies the absence of pain, fear, and hunger; enables a high level of biological functioning (i.e., normal growth, freedom from disease); and (more controversially) enables animals to experience positive emotional experiences such as comfort and contentment (Fraser et al. 1997).

It is possible for an animal to be in a state of poor health that does not impinge on its welfare or emotional state and that may even last for some time without the animal’s conscious awareness. For example, an animal might have a life-threatening aneurysm but be unaware of it and therefore not experience a negative emotional state. In the longer term, however, a breakdown in an animal’s ability to cope with its environment is likely to lead to adverse emotional states and poor welfare. Some of these cases may be quite minor and not give rise to significant ethical concerns; but prolonged or intense circumstances would compromise the animal’s welfare enough to warrant concern and also significantly affect the research results.

An attempt to graphically depict the relationship between distress and welfare is shown in Figure 2-2. Whereas minor perturbations (e.g., short-term restraint of a rodent) affect an animal’s welfare in terms of its moment-to-moment emotional state, they do not impair its adaptive capacity and thus do not cause distress. In contrast, a major homeostatic disruption (e.g., postsurgical infection), which causes measurable behavioral (withdrawal) and physiological (fever) changes that impair the adaptive capacity of the animal, is considered “distressful” and is indicative of “poor welfare”.

Onset of distress can be difficult to recognize. A safe assumption is to follow the fourth principle of the U.S. Government Principles for Utilization and Care of Vertebrate Animals used in Testing, Research and Teaching: “Proper use of animals, including the avoidance or minimization of discomfort, distress, and pain when consistent with sound scientific practices, is imperative. Unless the contrary is established, investigators should consider that procedures that cause pain or distress in human beings


For more information on the effects of housing on brain function or enrichment see Chapter 3. Additional information is contained in articles by the behaviorists Joseph Garner, Hanno Würbel, and Georgia Mason.

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement